The present invention concerns itself with modifications to grapple head assemblies. For simplicity of description the type of grapple assembly most commonly referred to within the specification shall be a bunching-type grapple assembly though it is envisaged that the present invention may also be incorporated onto other types of grapple assemblies.
Bunching-type grapple assemblies are commonly used in the logging industry, and the problems arising in this industry have been in the mind of the inventor during the development of this invention. In this industry grapples are commonly used for moving logs—often for loading onto the back of a logging truck, stacking for future use or processing, or loading into processing apparatus. Depending upon the type of processing apparatus (typically a de-limber), the grapple may have a further role insofar as dragging the log through the de-limbing apparatus. As de-limbing apparatus which includes means for driving the log is a substantially more expensive than non-driven types of de-limbing apparatus, it is not uncommon for grapples to also be used in the role of dragging logs through the de-limber. Accordingly, grapples used in the logging assembly can be used in a number of roles and consequently are subjected to quite a bit of abuse.
As it is often necessary to trim large logs into smaller segments for transport or processing, grapple design has evolved to include cut-off saws enabling a log to be trimmed after being set down by the grapple. This can provide a significant advantage as a single operator, being the person in charge of the grapple and the equipment to which it is attached, can also attend to the trimming of logs. The alternative is to employ an additional person whose sole purpose it is to trim the logs into smaller segments which must then be picked up and placed appropriately by the grapple in any event. Not only does this alternative employ more people (and hence less cost effective), it can also be slower in terms of throughput and can expose the ground operator to some risk. The consequence is that grapples with attached cut-off saws are very popular—particularly in smaller operations which cannot afford to employ additional staff, or whose total throughput may not warrant the hiring of additional staff for specific roles.
The standard design of grapples with a cut-off saw is to take a substantially standard grapple and to mount to the outside—typically to the front or back depending on orientation—a saw with motor assembly. Typically this is a chainsaw, so as to achieve the necessary length of cut exceeding a typical log's diameter. This is generally pivotally mounted toward one end of the grapple (e.g. left or right when viewing the grapple assembly from the front). Typically it is pivotally mounted to the outside of the grapple's head portion, and often in proximity to the pivot pins connecting a jaw to the head portion of the grapple assembly. There is typically additional drive means to drive the saw blades to pivot downwardly so as to cut through a log which may still be substantially held or cradled within the arms of the grapple assembly.
To the outside of the saw blade assembly is provided a saw motor—that is to say, the saw blade is positioned between the outside of the head portion, and the saw motor which extends outwardly from the grapple. The saw blade assembly and motor is very much a bolt-on type assembly added as an after thought to original grapple designs. While this design is very effective, it does suffer from a number of not insignificant problems in use.
Firstly, the motor and saw blade assembly are quite fragile. Heavy impact can seriously damage or destroy the exposed motor and saw blade assembly. At the very least, contact between the motor or saw blade assembly with obstacles, during use of the grapple assembly, can distort components and place the blade assembly out of alignment. This affects the ability of the equipment to cut through a log. To repair or replace components can be very expensive, and can also lead to significant downtimes in terms of operations. Such delays are not acceptable for most logging and processing operations as operation may be suspended until repairs are made, or ground staff hired to manually trim logs.
The art has sought to address this by providing protective frames and covers for the motor and blade assembly. However these have only been mildly effective at best. If one considers the typical environment of a logging operation, and the requirement for logs to be processed quickly, as well as the various roles that the grapple may be used for, it is not surprising that contact is made by the side of a grapple with various obstacles. Given also the average weight of the grapple is at least half a ton, and often higher, there is considerable momentum and kinetic energy to be dissipated when the grapple does encounter an object or obstacle. Accordingly, damage to saw mechanisms and associated componentry is quite common and remains an Achilles heel of this type of grapple assembly.
Additionally, the outside placing of the saw blade motor assembly tends to unbalance the grapple assembly, as well as exposing even further a vulnerable component. The increased offset weight of the saw motor, is not particularly desirable as it unbalances the assembly. The art has attempted to address this by the provision of counterweights on the opposite side. However this tends to increase the overall weight and hence reduce the lifting capacity of any apparatus using the grapple assembly. The provision of protective covers to protect the motor and saw blade further exacerbates this problems to the extent that they cannot be adequately compensated for by counterweights. Accordingly, at best, any protective covers or shielding is a compromise between weight and strength. Again this represents an unsatisfactory solution to a problem plaguing this type of grapple assembly within the industry.
Therefore there is a need for an improved grapple with cut-off saw design which is less susceptible to damage through impact, and ideally is also more centrally balanced.
It is an object of the present invention to address these problems.
It is also an object of the present invention to provide an alternative grapple assembly in which the saw motor is less susceptible to damage from impact.
It is a further objective of the present invention to propose a design for an improved grapple assembly which is more balanced in terms of its centre line when viewed from the end.
At the very least it is an object of the present invention to provide the public with a useful alternative.
Aspects of the present invention will be described by way of example only and with reference to the ensuing description.